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What is electromotive force and how is it different to potential difference?

The electromotive force or emf of a cell in a circuit is, for a start, not a force at all: it has the unit of volts. A good definition is ‘the power supplied by the cell per unit current through the cell’ or...
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Answered by Tom B. • Physics tutor
12917 Views

When do you use 'n choose k' and where does the formula come from?

When do you use n choose k ? Say you have n objects/elements, and each one can either be selected or not selected. ‘ n choose k ’ gives you the number of different ways in which you can end up with k selecte...
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Answered by Tom B. • Maths tutor
21694 Views

What is a simple way to classify the enthalpy of a reaction?

The evolution of heat from a reaction is often classified as being exothermic or endothermic, but how do you know which one it is in order to assign the appropriate sign? A simple way to be sure of which typ...
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Answered by Victor O. • Chemistry tutor
2710 Views

How do I start my Personal Statement for English Literature?

Most people are tempted to start with a quote; I would strongly advise against it. You only have a certain amount of space to spend discussing literature, so start off immediately by talking about it, straig...
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4757 Views

How do I structure my time for the essay?

Remember you have only 90 minutes to get through the ELAT, and structure accordingly. Be familiar with your strengths beforehand: are you more comfortable analysing prose or poetry? Spending too long making ...
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Answered by Pratyusha P. • ELAT tutor
3279 Views